Is a change in color when combining two substances normally a sign of a chemical change or a physical change?

Answer:

21% oxygen and 78%nitrogen

Explanation:

Answer:

Nitrogen and Oxygen

Explanation:

nitrogen - 78 %

oxygen - 21%

Answer:

Explanation:

The ionization energy is required to cause a gaseous atom or ion to release a electron.

Answer:8.334×10^-6 moles

Explanation:

a mole is 6.023×10^23

5.02×10^18 ÷ 6.023×10^23=8.33×10^-6

Answer:

U shaped vallies?

Explanation:

(i dont know if this was one of the options)

The law of conservation of mass states that

In any chemical reaction mass is neither created nor destroyed rather it remains conserved

Look the chemical reaction below

[tex]\\ \sf\longmapsto 2H_2+O_2=2H_2O[/tex]

Count the mass on both sides and simplify

Answer:

a

Explanation:

C. physical change

Explanation:

That's the answer

Answer:

The atomic mass

Explanation:

Answer: atomic mass

Answer:

Gold Iron Titanium Lithium

Explanation:

To find the force,

 ⇒ must know the force's formula ⇒ F = MA

Let's consider the information given:

Let's solve:

  [tex]F=MA=0.025kg*5m/s^2=0.125N[/tex]

Thus the force is 0.125N

Answer: 0.125N

Hope that helps!

The three-dimensional coordination number of the face-centered cubic arrangement  has a coordination number of 12 and contains 4 atoms per unit cell.

The coordination number, also known as ligancy, of a central atom in a molecule or crystal is the sum of all the atoms, molecules, or ions that are linked to it. This value is used in crystallography and materials science. A ligand is the ion, molecule, or atom that surrounds the center ion, molecule, or atom.

The number of atoms, ions, or molecules that a central atom or ion bears in a complex or coordination compound or in a crystal as its near neighbors is known as the coordination number, also known as ligancy.

In contrast to oxidation state, which is a number assigned to an element in chemical combination and represents the number of electrons lost or gained by an atom of that element in the compound, co-ordination number is the number of co-ordination bonds with which the ligands are bound to the central ion.

Thus, the face-centered cubic arrangement  has a coordination number of 12 and contains 4 atoms per unit cell.

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Answer:

An elastic collision.

Explanation:

When a ball is dropped to the ground, one of four things may happen: It may rebound with exactly the same speed as the speed at which it hit the ground. This is an elastic collision.

Answer:

Explanation:

This is just a ratio question. Factor of increase = 27.2 / 3.20 = 8.50

Answer:

Answer:

Q1= 9.42

Q2= 227 KJ

Q3= 31.4 KJ

Qt=269 KJ

Explanation:

First you have to find the heat needed to make ice at a temperature of -45 C to pass to a temperature of 0 C.

You're given the formula so all you have to do is replace by the data you're given (remember to make the Celsius, Kelvin by adding 273.15 to the Celsius since the magnitudes of temperature they're giving you in the constants are the Kelvin)

Q1= (2.093 J/gxK)(100 g)(45 K)

Q1=9418.5 J

Q1=9.4185 KJ≈9.42 Kj(you're asked to give your answer in KJ)

You know have to find the energy needed to liquify the ice, in other words you need to use the enthalpy of fusion to determine the energy that's being used, and since you have 100 grams of water, you only need to find the number of moles present in 100 grams of water by dividing the number of grams by the molar mass of water (18 g/mol) and then replace in the equation.

Q2=(5.56 mol)(40.7 KJ/mol)

Q2=227 KJ

You know have to find the energy needed to raise the temperature of water from 0 C to 75 C. You do the same thing as you did in the first step:

Q3=(4.184 J/gxK)(100 g/)(75K)

Q3=31380 J

Q3=31.38 KJ≈31.4 KJ

For the final step, you only add the Qs of each step:

9.42KJ+227KJ+31.4KJ= 267.82 KJ ≈ 267.8 KJ

Why do you use these procedures?

Well, you could simply have made a unique equation at first sight that involved the changes of temperature from -45 C to 75 C, but you have a phase change in the middle. Phase change keep temperature constant but they require heat from the surroundings in order to, in the case of ice, break the bonds that keep the molecules tight together.

This heat required from the surroundings is the Enthalpy of phase change, in this case enthalpy of fusion.

Using thermodynamics

[tex]\\ \sf\longmapsto Q=mc∆T[/tex]

[tex]\\ \sf\longmapsto Q=0.015(328)(4184)[/tex]

[tex]\\ \sf\longmapsto Q=20585.28J[/tex]

Answer:

Explanation:

Taking into account the definition of Avogadro's Number, the correct answers are:

1 mole of any element contains 6.023×10²³ atoms

1 mole of any compound contains 6.023×10²³ molecules

You have to know that Avogadro's Number or Avogadro's Constant is called the number of particles that make up a substance (usually atoms or molecules) and that can be found in the amount of one mole of said substance. Its value is 6.023×10²³ particles per mole.

Avogadro's number represents a quantity without an associated physical dimension, so it is considered a pure number that allows describing a physical characteristic without an explicit dimension or unit of expression.

Avogadro's number applies to any substance, because the number of elementary units in a mole of a substance is, by definition, a  constant that does not depend on the material or the type of particle considered.

So, in this case, the correct answers are:

1 mole of any element contains 6.023×10²³ atoms

1 mole of any compound contains 6.023×10²³ molecules

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Answer:

2) To find the atoms from the moles, you just multiply Avogadro's number (6.02 x 10^23) by the moles.

So 3.35 x (6.02 x 10^23) = 2.0167 x 10^24 atoms are in 3.35 moles of aluminum

3) If the question is asking under standard temperature and pressure, we know that if we divide the volume by the molar volume of a gas (which is 22.7 in standard temperature and pressure), we can get the moles.  

So 101.25L / 22.7 = 4.46 mol

4) We know that to find the moles, it is the mass divided by the molar mass. If we rearrange the equation to solve for mass, we have to multiply the moles by the molar mass to get there.

Nitrogen's (N) molar mass on the periodic table is 14g/mol, but since Nitrogen is a diatomic element, it would be N2 by itself. So multiply 14 by 2, which will give you 28g/mol. N2's molar mass is 28g/mol.

Now you multiply 13.7 moles by 28g/mol, which will give you 383.6g

Just did a few edits here, 4.46 for question 3 is in moles not L

Taking into account the definition of avogadro's number,

2. 3.35 moles of aluminum contains 2.018ײ⁴ atoms.

3. 4.52 moles of CO₂ gas are in a 101.25 L container filled with CO₂ gas.

4. 13.7 moles of N₂ contain 383.6 grams.  

Avogadro's Number is called the number of particles that make up a substance (usually atoms or molecules) and that can be found in the amount of one mole of said substance. Its value is 6.023×10²³ particles per mole. Avogadro's number applies to any substance.

Then you can apply the following rule of three: if 1 mole of aluminum contains 6.023×10²³ atoms, then 3.35 moles of aluminum contains how many atoms?

amount of atoms of aluminum= (6.023×10²³ atoms × 3.35 moles)÷ 1 mole

amount of atoms of aluminum=2.018ײ⁴ atoms

Finally, 3.35 moles of aluminum contains 2.018ײ⁴ atoms.

The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C are used and are reference values for gases. And in these conditions 1 mole of any gas occupies an approximate volume of 22.4 liters.

Then, you can apply the following rule of three: If by definition of the STP conditions 1 mole of CO₂ occupies a volume of 22.4 L, how many moles does 101.25 L occupy?

[tex]amount of moles of CO_{2} =\frac{101.25 Lx1 mole of CO_{2} }{22.4 L}[/tex]

amount of moles of CO₂= 4.52 moles

4.52 moles of CO₂ gas are in a 101.25 L container filled with CO₂ gas.

The molar mass of substance is a property defined as its mass per unit quantity of substance, in other words, molar mass is the amount of mass that a substance contains in one mole.

In this case, the molar mass of N₂ is 28 g/mole. So, you can apply the following rule of three:  If 1 mole of N₂ contains 28 grams, 13.7 moles of N₂ contain how much mass?

[tex]mass=\frac{13.7 moles x28 grams}{1 mole}[/tex]

mass= 383.6 grams

13.7 moles of N₂ contain 383.6 grams.

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Answer:

D

Explanation:

Given that the molar mass of NaCl is 58.44 g/mol, we want to determine the molarity of a solution that contains 87.75 g of NaCl in 500. mL of solution.

Recall that molarity is given by:

[tex]\displaystyle \text{M} = \frac{\text{ mols solute}}{\text{ liters soln.}}[/tex]

Therefore, we can convert the amount of NaCl in the solution to moles of NaCl and the volume from milliliters to liters:

[tex]\displaystyle \begin{aligned} \text{M} & = \frac{(87.75 \text{ g NaCl})}{(500. \text{ mL soln.})} \cdot \frac{1 \text{ mol NaCl}}{58.44 \text{ g NaCl}} \cdot \frac{1000 \text{ mL soln.}}{1 \text{ L soln.}} \\ \\ & = 3.00\text{ } \frac{\text{mol NaCl}}{\text{ L soln.}} \\ \\ & = 3.00 \text{ M} \end{aligned}[/tex]

Hence, our answer is D.

Answer:

Historically, wood was the main source of U.S. energy until the mid-1800s and was the only commercial-scale renewable source of energy in the United States until the first hydropower plants began producing electricity in the 1880s.

The Advantages of Renewable Energy Resources-A Fuel Supply That Never Runs Out.Zero Carbon Emissions.Cleaner Air and Water.Disadvantages of Renewable Energy-he Electricity Generation Capacity is Still Not Large Enough.Renewable Energy Can be Unreliable.

First, we need to take advantage of the world's abundant natural gas resources and reduce coal consumption;

Second, governments must support development of carbon capture and storage technology to make fossil fuel use cleaner;

Explanation:

Answer: In the core of the Sun hydrogen is being converted into helium. This is called nuclear fusion. It takes four hydrogen atoms to fuse into each helium atom. During the process some of the mass is converted into energy.

A 1.00 mole of Sulfuric acid (H₂SO₄) contains the largest number of atoms (7 atoms/molecule). Option B is correct.

To determine which of the given compounds contains the largest number of atoms in 1.00 mole, we need to consider the number of atoms in each compound.

1.00 mole of NH₃ contains:

1 mole of N atoms (1 atom/molecule)

3 moles of H atoms (3 atoms/molecule)

Total atoms = 1 + 3 = 4 atoms/molecule

1.00 mole of H₂SO₄ contains:

2 moles of H atoms (2 atoms/molecule)

1 mole of S atoms (1 atom/molecule)

4 moles of O atoms (4 atoms/molecule)

Total atoms = 2 + 1 + 4 = 7 atoms/molecule

1.00 mole of HBr contains:

1 mole of H atoms (1 atom/molecule)

1 mole of Br atoms (1 atom/molecule)

Total atoms = 1 + 1 = 2 atoms/molecule

Therefore, 1.00 mole of H₂SO₄, contains the largest number of atoms.

Hence, B. is the correct option.

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The boiling point of salt water is greater than that of fresh water hence the electrostatic forces between molecules in salt water is greater than that between the molecules in salt water.

Fresh water contains does not contain dissolved solutes like salt water. Salt water contains a lot of dissolved mineral salts making the salt water to be rich in ions.

Generally, the boiling points of substances can serve as a measure of the strength of electrostatic forces between molecules in either kind of water. We will easily find the that the boiling point of salt water is far higher than that of fresh water indicating greater electrostatic forces between molecules in salt water than between molecules in fresh water.

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Answer:

B

Explanation:

We can convert strontium-82 to rubidium-82 by positron emission.

The three main fundamental subatomic particles in an atom are;

In a neutral atom, the number of protons is always equal to the number of electrons.

In strontium-82, there are 44 neutrons, 38 electrons and 38 protons. In rubidium-82, there are 45 neutrons, 37 electrons and 37 protons. We can convert  strontium-82 to rubidium-82 by positron emission.

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Answer: A change in color is not always a chemical change. If one were to change the color of a substance in a non-chemical reaction scenario, such as painting a car, the change is physical and not chemical.

Solid → Liquid: Melting

Solid → Gas: Sublimation

Liquid → Gas: Vaporization

Gas → Liquid: Condensation

Explanation: